The invention relates to a method for robot-controlled cutting of workpieces to be joined by means of laser radiation that is being focused onto a first workpiece whose cut contour is assembled and joined with a second workpiece.
Such a method is known in general. It is carried out conventionally with buckling arm robots that, based on their low adjusting frequency of approximately 10 Hz for all axes, have significant impression for cutting and welding. In addition, there are impressions as a result of the mechanical manufacture of the robot parts, of the employed encoders, and as a result of the machine-internal coordinate system that deviates from an ideal coordinate system. Moreover, dynamically caused impressions of the focal point position are present. Depending on the gear configuration and amount of teach points, a path repetition precision of only approximately +/−0.1 to +/−0.4 mm in any of the three coordinate directions is achieved for approximately 5 m/min. The resulting precision range is +/−0.1×sheet metal thickness. It would be necessary to bring the precision for cutting sheet metal by means of robots to a precision of +/−0.05 ×sheet metal thickness in order to prevent a seam collapse for welding without welding additives. Moreover, radii of less than 50 mm cannot be welded with the known method because the robot control correction is too slow.
Moreover, it is known (IP 901 875 A1) to control a laser beam by means of one or several moved mirrors on a robot hand such that this robot hand is maintained in a predetermined position during machining. The focus can then be positioned with higher precision on the workpiece in comparison to the robot control. The processing width to be achieved of approximately 50 mm is however completely unsatisfactory, in particular, for manufacturing tube frame structures in the automobile construction sector.